Browsing by Author "Loren Price"

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    Complement-mediated muscle cell lysis: A possible mechanism of myonecrosis in anti-SRP associated necrotizing myopathy (ASANM)
    (2013-09-16) Arada Rojana-udomsart; Chalermchai Mitrpant; Christine Bundell; Loren Price; Yue Bei Luo; Victoria Fabian; Steve D. Wilton; Peter Hollingsworth; Frank L. Mastaglia; University of Western Australia; Mahidol University; Queen Elizabeth II Medical Centre Trust; Royal Perth Hospital
    The mechanism of necrotizing myopathy associated with antibodies to signal recognition particle (SRP) remains unclear. We investigated the effect of anti-SRP. +. serum and complement on cell viability in myoblast cultures. Cell viability was only slightly reduced by incubation with anti-SRP. +. serum compared with control serum. However, the addition of fresh complement resulted in a marked reduction in cell survival. Surface immunostaining for SRP, C3c and C5b-9 was demonstrated in cultures pre-incubated with anti-SRP. +. serum and complement, and in muscle biopsies from patients with myopathy. These findings provide further support for a complement-dependent antibody-mediated mechanism in anti-SRP associated myopathy. © 2013 Elsevier B.V.
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    Improved Antisense Oligonucleotide Design to Suppress Aberrant SMN2 Gene Transcript Processing: Towards a Treatment for Spinal Muscular Atrophy
    (2013-04-22) Chalermchai Mitrpant; Paul Porensky; Haiyan Zhou; Loren Price; Francesco Muntoni; Sue Fletcher; Steve D. Wilton; Arthur H M Burghes; University of Western Australia; Mahidol University; Ohio State University Medical Center; UCL
    Spinal muscular atrophy (SMA) is caused by loss of the Survival Motor Neuron 1 (SMN1) gene, resulting in reduced SMN protein. Humans possess the additional SMN2 gene (or genes) that does produce low level of full length SMN, but cannot adequately compensate for loss of SMN1 due to aberrant splicing. The majority of SMN2 gene transcripts lack exon 7 and the resultant SMNΔ7 mRNA is translated into an unstable and non-functional protein. Splice intervention therapies to promote exon 7 retention and increase amounts of full-length SMN2 transcript offer great potential as a treatment for SMA patients. Several splice silencing motifs in SMN2 have been identified as potential targets for antisense oligonucleotide mediated splice modification. A strong splice silencer is located downstream of exon 7 in SMN2 intron 7. Antisense oligonucleotides targeting this motif promoted SMN2 exon 7 retention in the mature SMN2 transcripts, with increased SMN expression detected in SMA fibroblasts. We report here systematic optimisation of phosphorodiamidate morpholino oligonucleotides (PMO) that promote exon 7 retention to levels that rescued the phenotype in a severe mouse model of SMA after intracerebroventricular delivery. Furthermore, the PMO gives the longest survival reported to date after a single dosing by ICV. © 2013 Mitrpant et al.
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    A novel morpholino oligomer targeting ISS-N1 improves rescue of severe spinal muscular atrophy transgenic mice
    (2013-03-01) Haiyan Zhou; Narinder Janghra; Chalermchai Mitrpant; Rachel L. Dickinson; Karen Anthony; Loren Price; Ian C. Eperon; Stephen D. Wilton; Jennifer Morgan; Francesco Muntoni; UCL Institute of Child Health; Mahidol University; University of Western Australia; University of Leicester
    In the search for the most efficacious antisense oligonucleotides (AOs) aimed at inducing SMN2 exon 7 inclusion, we systematically assessed three AOs, PMO25 (-10,-34), PMO18 (-10,-27), and PMO20 (-10,-29), complementary to the SMN2 intron 7 splicing silencer (ISS-N1). PMO25 was the most efficacious in augmenting exon 7 inclusion in vitro in spinal muscular atrophy (SMA) patient fibroblasts and in vitro splicing assays. PMO25 and PMO18 were compared further in a mouse model of severe SMA. After a single intracerebroventricular (ICV) injection in neonatal mice, PMO25 increased the life span of severe SMA mice up to 30-fold, with average survival greater by 3-fold compared with PMO18 at a dose of 20 μg/g and 2-fold at 40 μg/g. Exon 7 inclusion was increased in the CNS but not in peripheral tissues. Systemic delivery of PMO25 at birth achieved a similar outcome and produced increased exon 7 inclusion both in the CNS and peripherally. Systemic administration of a 10-μg/g concentration of PMO25 conjugated to an octaguanidine dendrimer (VMO25) increased the life span only 2-fold in neonatal type I SMA mice, although it prevented tail necrosis in mild SMA mice. Higher doses and ICV injection of VMO25 were associated with toxicity. We conclude that (1) the 25-mer AO is more efficient than the 18-mer and 20-mer in modifying SMN2 splicing in vitro; (2) it is more efficient in prolonging survival in SMA mice; and (3) naked Morpholino oligomers are more efficient and safer than the Vivo-Morpholino and have potential for future SMA clinical applications. © 2013, Mary Ann Liebert, Inc.